1. Doctor, Transportation College, Dalian Maritime Univ., Dalian, China 116026.
2. Doctor, School of Mechanical Engineering, Dalian Univ. of Technology, Dalian, China 116024; formerly, Transportation College, Dalian Maritime Univ., Dalian, China 116026.
3. Professor, Transportation College, Dalian Maritime Univ., Dalian, China 116026.
4. Doctor, School of Transportation Engineering, Tongji Univ., Shanghai, China 200092 (corresponding author).